After a long period of procrastination, with the parts sitting around, I finally built my own take on Brad Sarno's Freeloader. One JFET, two caps, four resistors, a 500K audio taper pot. Add a diecast box, a couple of 1/4 " jacks, a battery clip and terminal, a knob and a leg clip and a piece of circuit board and the total parts cost was maybe 40-45 bucks CDN.
Well, now I really know just why the Freeloader is such a great box, and vastly superior to the passive tone control on some steels for taming harsh top end.
The passive tone circuit kills the harshness, but also all your top end. The Freeloader type buffer smooths the resonant peak without killing all the sparkle.
If you are reading this Brad, I'm also liking the pickup load in the 150K area. Pickup is a 12 string Tonealigner.
If anyone is interested, I'll post the circuit I used here. It is about time I learned how to post images anyway, after eight years on this forum. _________________Excel Superb U12, Heritage H575, MIJ Squier tele, Hwy 1 Strat, modified Deluxe Reverb RI, Cube 80XL, self built acoustics & mandolins

Robert Parent

From:Savage, MN

Posted 19 Nov 2017 1:42 pm

Hi Chris,

Please post your schematic as I for one would be interested.... I built the current buffer that I am using. It is based on a LF353 op amp, it works great, but always like to try different ideas.

Last edited by Chris Reesor on 22 Nov 2017 9:25 pm; edited 3 times in total

Robert Parent

From:Savage, MN

Posted 19 Nov 2017 3:02 pm

Thanks Chris, I'll give it a try.

Jon Light

From:Saugerties, NY

Posted 19 Nov 2017 3:03 pm

I'm trusting that you did not just reverse engineer the Freeloader, right?

Chris Reesor

From:British Columbia, Canada

Posted 19 Nov 2017 3:36 pm

No, Jon, I just used a basic JFET buffer circuit I found on the web, and added a variable resistive load right across the pickup. The basic idea is Brad's, I believe, at least that is where I got the idea. How closely this corresponds to the innards of a Sarno Freeloader, I don't know. But it does work well, and whether it would be better with another transistor in terms of hiss, it will take ears with better high frequency response than mine to say. Forty years of driving heavy trucks does take a toll.
Peace._________________Excel Superb U12, Heritage H575, MIJ Squier tele, Hwy 1 Strat, modified Deluxe Reverb RI, Cube 80XL, self built acoustics & mandolins

Jon Light

From:Saugerties, NY

Posted 19 Nov 2017 3:38 pm

Cool. I hoped not. Thanks for the answer.

ajm

From:Los Angeles

Posted 20 Nov 2017 9:30 am

I looked at the schematic.

At the maximum pot setting, the voltage input to the FET circuit will be divided by around 10:1.
I would think that you would notice a large volume drop.
In addition, because of the hearing characteristics of our ears, you may also notice a perceived drop in high frequencies.

At the minimum pot setting, the input impedance to the circuit is around 47K. Assuming that you are feeding the circuit directly from the guitar, that will probably load the pickup enough to get rid of some highs.

Discuss.

Scott Duckworth

From:Etowah, TN Western Foothills of the Smokies

Posted 20 Nov 2017 11:00 am

I had posted a schematic here based on the author hand drawn first version, but since so many changes were made, I decided it best to delete it. Sorry._________________(1) E6 Rogue lap steel, (1) A6 Rogue lap steel, Li'l Izzy, Zoom MS-50G Effects Pedal into a Berhinger mixer and Harbinger V2112 speaker(s).

I may, in fact, be nuts. However, I am screwed onto the right bolt... Jesus!

Last edited by Scott Duckworth on 23 Nov 2017 4:13 am; edited 1 time in total

Chris Reesor

From:British Columbia, Canada

Posted 20 Nov 2017 11:07 amOops!

Yes, ajm, there is an error in my quickie schematic. Input jack is actually connected to the .1 mfd. cap with the pot and 47K resistor directly across the input jack terminals.
Good spot. Thanks. I'll post a corrected schematic when I find my camera (!) and figure out how to post images here.

Edit: I see Scott was posting a schematic while I was typing. Could you please correct the circuit as I have described?
Much obliged._________________Excel Superb U12, Heritage H575, MIJ Squier tele, Hwy 1 Strat, modified Deluxe Reverb RI, Cube 80XL, self built acoustics & mandolins

ajm

From:Los Angeles

Posted 20 Nov 2017 2:56 pm

Here's what I think you want corrected on Scott's schematic.

1) That resistor should be 47K, NOT 4.7K.

2) The pot and the 47K are connected in series, not parallel.
That would vary the resistance from 47K at minimum to 547K at maximum.

3) The input jack is connected to the junction of the 47K/500K series and the 0.1 uF cap.

If any of this is not correct please advise.

If all of this is correct, what DC voltage do you measure on the source of the FET?
Ideally I think you want it to be half of the supply voltage.

Chris Reesor

From:British Columbia, Canada

Posted 20 Nov 2017 7:32 pm

ajm, the corrections you suggest sound right.
I didn't take any voltage readings on this circuit before putting it together for testing, however if my theory is correct,the gate should be at roughly 50% of the battery voltage (10 % tolerance resistors in the bias divider), and the source at that voltage minus .6 V since the source-gate junction is reverse biased.
I am going to build another one and install it in the guitar, since there is already a tone control with a switch to take it out of the circuit when fully CCW. Lots of room under there for a little shielding box and a battery bag.
OK, back to making supper. _________________Excel Superb U12, Heritage H575, MIJ Squier tele, Hwy 1 Strat, modified Deluxe Reverb RI, Cube 80XL, self built acoustics & mandolins

Brad Sarno

From:St. Louis, MO USA

Posted 21 Nov 2017 7:48 amRe: homebrew variable load buffer

Chris Reesor wrote:

After a long period of procrastination, with the parts sitting around, I finally built my own take on Brad Sarno's Freeloader. One JFET, two caps, four resistors, a 500K audio taper pot. Add a diecast box, a couple of 1/4 " jacks, a battery clip and terminal, a knob and a leg clip and a piece of circuit board and the total parts cost was maybe 40-45 bucks CDN.
Well, now I really know just why the Freeloader is such a great box, and vastly superior to the passive tone control on some steels for taming harsh top end.
The passive tone circuit kills the harshness, but also all your top end. The Freeloader type buffer smooths the resonant peak without killing all the sparkle.
If you are reading this Brad, I'm also liking the pickup load in the 150K area. Pickup is a 12 string Tonealigner.
If anyone is interested, I'll post the circuit I used here. It is about time I learned how to post images anyway, after eight years on this forum.

Nice work! Yeah, 150kOhm load is totally usable and often a sweet spot. I definitely find myself dialing the load down that low at times and with certain pickups too. I remember years ago checking out one of Tom Brumley's ZB volume pedals, and it had a military spec Clarostat potentiometer in it that was 100k audio taper. So he was working with a loading of 100k, FAR lower than most anyone else uses. And he made it work. He had such a fat, warm tone yet with plenty of clarity. I think I personally tend to operate in the 180k to 300k range mostly when it comes to load impedance values. I can't remember where I was with the Tonealigner when I had it in my guitar.

Brad

Chris Reesor

From:British Columbia, Canada

Posted 21 Nov 2017 9:13 am

Thanks for the comment ,Brad. Too bad I didn't pay attention to where Greg Leisz had his Freeloader set with his 12 string Tonealigner when I saw him play a small club with Bill Frisell a few years ago. He was using a Fender DeVille , and the result was warm and full but certainly didn't lack clarity.
The observation about Brumley and his 100k volume pot just emphasizes the point about the overall effect of pickup load on your sound, I think.
I wonder about how an active pickup similar to an EMG would work for PSG. With low inductance and distributed capacitance, the pickup resonance could be raised well above the frequency band we are working with, I think._________________Excel Superb U12, Heritage H575, MIJ Squier tele, Hwy 1 Strat, modified Deluxe Reverb RI, Cube 80XL, self built acoustics & mandolins

ajm

From:Los Angeles

Posted 22 Nov 2017 8:47 am

A couple more comments (open to correction/criticism/etc).....

1) I'd add a resistor to ground on the output.
If you don't have one, you might get a large pop when you connect it up due to DC voltage charging on the capacitor.
Value?
Maybe 10K or 100K or 1 Meg or ??????

2) This is a unity gain, or less, buffer.
There is no amplification here.
Then again, amplification is not what we intend on.

3) The biasing will result in less than symmetrical clipping at the output if you ever drive it hard enough.
This may or may not matter.

4) I'd add a reverse biased diode from V+ to ground in the event that you ever connect a battery up backwards (even momentarily).

Georg Sørtun

From:Mandal, VA, Norway & Weeki Wachee, FL, USA

Posted 22 Nov 2017 3:20 pm

ajm wrote:

4) I'd add a reverse biased diode from V+ to ground in the event that you ever connect a battery up backwards (even momentarily).

That's only useful when either a quick fuse or (preferable) a low-value series resistor is added on the V+ side - with the reverse connected diode after it. Otherwise a reversed battery will just blow the reversed diode along with other components.

(One can start a fire with the energy from a 9Volt battery, so get the protective circuit right.)

Dave Hepworth

From:West Yorkshire, UK

Posted 22 Nov 2017 4:06 pm

Hi,
Could you please post an amended circuit diagram of the suggested mods that work on this.Also if I wanted to use a J201 in this circuit ,what would the pin out be on the circuit please ,with annotation/ alignment .
Regards Dave

Chris Reesor

From:British Columbia, Canada

Posted 22 Nov 2017 10:05 pm

I have posted a new link to the corrected schematic in the third post of this thread.
Dave, the J201 has the same pinout as MPF102, which I used simply because my nephew gave me several. I added a little pinout drawing to the schematic.
I'm wondering whether protection for reversed battery polarity is necessary here; the 3.3k resistor would limit the channel current to around 3mA, well within the device limits. The forward biased G-S junction current would be limited by the 2.2 M bias resistor to a few microamps.
I'll have to whip up another one, hook up the battery backwards and see if the transistor survives.
About the suggested resistor across the output circuit: So far, I have only run this thing into my passive Goodrich VP, so not an issue. However, we will see what happens when I try some dirt boxes before the VP.
I'm not hearing any clipping with my hardest picking.
Yes, it might clip asymmetrically, which is not necessarily a bad thing (watch a Champs' output waveform on a scope as you drive it into distortion some time) but I doubt you will get it there with even the hottest passive steel pickup._________________Excel Superb U12, Heritage H575, MIJ Squier tele, Hwy 1 Strat, modified Deluxe Reverb RI, Cube 80XL, self built acoustics & mandolins

Georg Sørtun

From:Mandal, VA, Norway & Weeki Wachee, FL, USA

Posted 23 Nov 2017 1:43 am

I don't see the need for a reversed voltage protection for that circuit. If protection is wanted I would rather take the about .7 Volt drop by having a diode in series between battery + terminal and V+.

As for a resistive load over the output terminal: 1Mohm to GND to pull the capacitor down and reduce/eliminate "pops", certainly wouldn't hurt. Most effect units has a 500K to 1M input impedance, amps more in the 220K to 500K range, but that do not always represent a resistive load for connected units.

Dave Hepworth

From:West Yorkshire, UK

Posted 23 Nov 2017 9:50 am

Hi Chris,
Thanks for the ammended circuit diagram .I didn't see it on 3rd reply !!
I have quite a few J201 s and have built a buffer and guitar treble booster with them.This project looks interesting .......a buffer with tone adjustment ,controlled by altering the impedance ......am I correct?
Regards Dave

Scott Duckworth

From:Etowah, TN Western Foothills of the Smokies

Posted 23 Nov 2017 3:42 pm

OK, I redrew the schematic for you in my computer, hopefully it is right...

I may, in fact, be nuts. However, I am screwed onto the right bolt... Jesus!

Last edited by Scott Duckworth on 24 Nov 2017 2:40 pm; edited 2 times in total

Chris Reesor

From:British Columbia, Canada

Posted 23 Nov 2017 7:08 pm

That's got it, Scott.Thank you.
I did find my camera, just a few minutes ago. I seem to be getting better and better at hiding things from myself lately; must be a sign of "maturity" -
I should note that if you hook the pot up correctly, fully ccw will show the pickup a 47k load, mid rotation about 100k, and fully cw about 550k.
It probably wouldn't be a bad idea to add a 1 meg resistor across the output jack as ajm and Georg suggest; I'll add it to the next iteration of this circuit, to be built into my Excel.
Excelsior!_________________Excel Superb U12, Heritage H575, MIJ Squier tele, Hwy 1 Strat, modified Deluxe Reverb RI, Cube 80XL, self built acoustics & mandolins

ajm

From:Los Angeles

Posted 23 Nov 2017 8:27 pm

Diode protection: I like Georg's idea of putting a diode in series with the V+ line. Probably easier and fewer parts than what I originally suggested.

The "problem" is with the battery connections on the left to the input jack as they are drawn schematically.
If you take away the verbage for the Ring/Tip, and the verbage down below about the battery, whomever builds this will build it wrong. (The same applies if someone just looks at the "picture" and doesn't read the notes.)

"Picture wise" you show the tip of a plug being connected to the -9 VDC, and the ground sleeve of the plug connecting to the input of the circuit.

If you pull up virtually any effect schematic on line you'll see what I mean.

True, as long as whomever builds it reads every note they'll probably be fine. If they follow the picture and don't read it carefully they'll have a problem.
From my experience in electrical engineering, the less that someone is required to think about what they're doing it's usually for the better.

I had to look up Veroboard, since I hadn't heard the term in decades. I actually built mine on a small piece of some knockoff Asian version that I had around._________________Excel Superb U12, Heritage H575, MIJ Squier tele, Hwy 1 Strat, modified Deluxe Reverb RI, Cube 80XL, self built acoustics & mandolins